Range change transmission for vehicles

ABSTRACT

In a range change transmission for vehicles which is designed as planetary transmission (2), a sun gear (3) is driven by a drive shaft (4) of an added basic transmission while a planet carrier (8) of the planetary transmission (2) is rigidly connected with an output shaft (9) of the range change transmission. To engage a low ratio group of the range change transmission, a ring gear (6) is connected with a transmission casing (1) by means of a sliding sleeve (25). In a direct through drive, the sliding sleeve (25) connects the ring gear (6) with a planet carrier (8). The construction costs should be reduced by using a single-piece synchronizer ring (22), the single-piece synchronizer ring which is effective for both shift directions cooperating by both its friction faces (23) with bevel faces (18 and 19) on the transmission casing (1) and on the planet carrier (8).

The invention concerns a range change transmission for vehicles which is designed as a planetary gear having a sun wheel rigidly situated on an output shaft of a main transmission, a planet carrier rigidly connected with an output shaft of the range change transmission and a ring gear which, via a separating clutch concentrically situated with respect to the output or drive shaft, is connectable in a switching step to low ratio of the range change transmission with a transmission casing and in a direct through drive with a drive or output element, said separating clutch having a synchronizing device and an axially movable sliding sleeve whose gearing in two axial end positions of said sliding sleeve can be thrown into gear with a coupling gear respectively on the transmission housing or on the drive or output element.

BACKGROUND OF THE INVENTION

A range change transmission of said kind has been disclosed in DE-A 33 20 431. There the separating clutch has a synchronizing device with two synchronizer rings which respectively cooperate with a bevel surface on the transmission casing and with a bevel surface on a clutch ring rigid with the output shaft.

The invention is based on the problem of reducing the costs for a synchronizing device used on a range change transmission of the above kind.

SUMMARY OF THE INVENTION

According to the invention, said problem is solved by the fact that the synchronizing device has a single-piece synchronizer ring which with both friction faces cooperates with bevel surfaces situated on the transmission casing and on the input or output element. The bevel faces, which form an obtuse angle, have in addition a small axial distance between them. The single-piece synchronizer ring is provided with two friction faces which extend parallel with the bevel faces. A low cost is needed to produce such a synchronizer ring.

According to the invention, lubricant discharge openings must be provided in at least one of the bevel faces. Lubricant slipping from the planetary transmission to the oil sump in the area of the sliding sleeve can, in this manner, flow out again from the synchronizer device via a gap existing between the bevel faces and the lubricant discharge openings.

In addition, according to the invention, between the sliding sleeve and the synchronizer ring can be situated a ring spring which, upon axial movement of the sliding sleeve, moves the synchronizer ring for synchronization against the respective bevel faces. In another embodiment of the invention according to the invention, the planet carrier serving as output element must have a collar axially projecting over a support of planet bolts and on which a clutch body is rigidly situated over a gearing. In this manner the clutch body, upon which the bevel face is also provided, can be designed as a replaceable part. In the same manner it is possible, according to the invention, to guide rigidly on the transmission casing via a gearing a clutch body coordinated with the transmission casing.

The invention also covers two alternative possibilities of the axial movement of the synchronizer ring for synchronization. According to the invention, ramp-like pressure pieces are situated in a U-shaped recess of the synchronizer ring. Said pressure pieces are axially moved by pressure bolts and, in their end position, exert an axial force upon the synchronizer ring. According to the invention, two pressure pieces, each one of which acts in a direction of movement of the shifting operation, can be coordinated with each pressure bolt.

The invention is not limited to the combination of features of the claims. Other possible logical combinations result for the expert from the claims and separate features of the claims according to the exiting problem.

For further explanation of the invention, attention is drawn to the drawings in which an embodiment is shown in simplified manner. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section through a range change transmission with a separating clutch having a single-piece synchronizer ring;

FIG. 2 is a partial view from FIG. 1 in which one sliding sleeve of the separating clutch is axially moved to its left end position;

FIG. 3 is a partial view from FIG. 1 in which the sliding sleeve is again moved to its neutral position; and

FIG. 4 is a partial view from FIG. 1 in which the sliding sleeve is axially moved to its right shift position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Designated in FIG. 1, with a 1, is a transmission casing which carries in its interior a planetary gear 2 that serves as range change transmission. On the input side of the planetary gear 2 is a sun gear 3 which is rigidly connected with an output shaft 4 of a main transmission not shown. Other structural elements of the planetary gear 2 are planet gears 5, of which only one can be seen in the drawing, and a ring gear 6. The planetary gears 5, which are meshed into gear with both the sun gear 3 and with the ring gear 6, are supported over planet bolts 7 of a planet carrier 8. The planet carrier 8 is, in turn, rigidly connected with an output shaft 9 of the range change transmission which extends from the transmission casing 1 and is connected via a prop shaft 10 with a drive axle of the vehicle, not shown in detail.

An annular clutch body 11 which has a coupling gearing 12 by means of which it is also rigidly passed into the transmission casing 1 is fastened to the transmission casing 1. A second clutch body 13, which has an internal gearing 14 and an external gearing 15, is fastened to the planetary carrier 8. The second clutch body 13 is rigidly situated, by means of its internal gearing 14, on an axially projecting collar 8A of the planet carrier 8.

Both clutch bodies 11 and 13, have collars 16 and 17, pointing in axial direction and extending coaxially with respect to the output shaft 9, on which bevel faces 18 and 19 are provided. A gap 20 extends between the collars 16 and 17 and at least one lubricant discharge opening 21 leads from the bevel face 18 through the collar 16.

On the bevel faces 18 and 19 is positioned a single-piece synchronizer ring 22 which has friction faces 23 extending parallel with the bevel faces and, on its external periphery, locking gearings 24 adjacent both coupling gearings 12 and 15. On the synchronizer ring 22 is overhung a sliding sleeve 25, which has an internal coupling gearing 26 and in addition an external gearing 27 is rigidly passed into a gearing 28 of the ring gear 6. The sliding sleeve 25, which by means of a shift fork not shown in detail can be moved from its neutral position shown in FIG. 1 to shift positions, has radial pressure bolts 29 which are spring loaded in the direction of the synchronizer ring 22. Said pressure bolts cooperate with ramp-like pressure pieces 30 provided in a recess 31 made on the external periphery of the synchronizer ring 22. Here the recess is limited in an axial direction by abutment faces 32 on the end faces.

If the sliding sleeve 25 is in its position to the right, the ring gear 6 is rigidly connected with the transmission casing by the sliding sleeve 25 and the clutch bodies 11, whereby the range change transmission is in a low ratio. If the sliding sleeve 25 is moved to the left shift position by an axial movement, then it connects the planet carrier 8 with the ring gear 6 via the second clutch body 13, whereby a direct through drive of the range change transmission occurs. Only said two shift positions exist for the range change transmission whose function will be explained herebelow once more with reference to FIG. 1 to 4: In FIG. 1, the sliding sleeve 25 is moved to the left from the low ratio shift position of the range change transmission, the pressure bolts 29 abutting on the pressure pieces 30, which are moved within the recess 31, and finally come to abut on the end-face abutment surface 32, whereby there is exerted, upon the synchronizer ring 22, an axial force which produces a frictional action between the friction face 23 thereof and the bevel face 18. In another axial movement of the sliding sleeve 25, the inner coupling gearing 26 thereof is traversed by the locking gearing 24 of the synchronizer ring 22 and thrown in gear with the coupling gearing 15. This position of the sliding sleeve is shown in FIG. 2.

If, as shown in FIG. 3, the sliding sleeve 25 should now be moved from said shift position again to the low ratio position of the range change transmission, then the pressure bolt 29 first carries along the pressure piece 30 inside the recess 31 until it comes to abut on the opposite abutment face 32 on the end-face side. Since the spring-loaded pressure bolt 29 is moved along on the inclined plane of the respective pressure piece 30, the axial force transmitted to the synchronizer ring 22 again increases. Thereby a friction torque again becomes effective between the synchronizer ring 22 and the bevel face 19. If the ring gear is completely braked over the synchronizer ring 22, then the locking action of the locking gearing 24 subsides and the sliding sleeve 25 is thrown in gear by its internal coupling gearing 26 with the coupling gearing 12 of the clutch body 11. In this position, the pressure bolt 29 again has run past the ramp-like pressure piece 30.

Instead of using the spring-loaded pressure bolts 29 and the ramp-like pressure pieces 30, it is also possible to provide, within the recess 31 ring, springs which cooperate with inclined planes disposed on the sliding sleeve.

Reference Numerals

1 transmission casing

2 planetary gear

3 sun wheel

4 output shaft

5 planetary gears

6 ring gear

7 planet bolts

8 planet carrier

8A axial collar

9 output shaft

10 prop shaft

11 clutch body

12 coupling gearing

13 second clutch body

14 internal gearing

15 external coupling gearing

16 collar

17 collar

18 bevel face

19 bevel face

20 gap

21 lubricant discharge opening

22 synchronizer ring

23 friction face

24 locking gearing

25 sliding sleeve

26 internal coupling gearing

27 external gearing

28 gearing of 6

29 pressure bolt

30 pressure piece

31 recess

32 end-face abutment faces 

We claim:
 1. A range change transmission for a vehicle designed as planetary transmission (2), said range change transmission comprising:a sun gear (3) being rigidly supported adjacent one end of an output shaft (4) of a main transmission; a planet carrier (8), carrying planet gears, being rigidly connected to an output shaft (9) of said range change transmission; a separating clutch having a synchronizing device and an axially movable sliding sleeve (25); a ring gear (6) being concentrically disposed with respect to said output shaft (9) with said ring gear (6) being connectable, via said separating clutch, with a transmission casing (1) to provide a first ratio of said range change transmission and said ring gear (6) being connectable, via said separating clutch, with said output element (8 or 9) to provide a second ratio of said range change transmission; a gearing (26), supported by said sliding sleeve (25), being engageable with a coupling gear (12) supported by said transmission casing (1) when said sliding sleeve (25) is in a first axial end position, and said gearing (26) being engageable with a coupling gear (12) supported by said output element (8 or 9) when said sliding sleeve (25) is in a second axial end position; wherein said synchronizing device comprises a single-piece synchronizer ring (22) with two friction surface (23), one of said two friction surface (23) cooperates with a mating bevel surface (19) of said transmission casing (1) and the other of said two friction surfaces (23) cooperates with a mating bevel surface (18) of said output element (8 or 9); radial pressure members (29) are supported by said sliding sleeve (25) and spring loaded in a direction toward said synchronizer ring (22); ramp-like pressure pieces (30) are supported on the external periphery of said synchronizer ring and are axially movable in recesses (31) formed in said synchronizer ring, and said pressure members (29) exert an axial force upon said synchronizer ring (22) in both axial directions of movement of said sliding sleeve (25).
 2. A range change transmission according to claim 1, wherein at least one lubricant discharge opening (21) is provided in at least one of said bevel surfaces (18, 19).
 3. A range change transmission according to claim 1, wherein a ring type spring is disposed, within a recess (31) of said synchronizer ring (22), between said sliding sleeve (25) and said synchronizer ring (22).
 4. A range change transmission according to claim 1, wherein said planet carrier (8) has a collar (SA), including an external gearing, which supports a clutch body (13) via an internal gearing (14) of said clutch body (13).
 5. A range change transmission according to claim 1, wherein a clutch body (11) is engaged with said transmission casing (1) via a gearing, and an extension of the gearing of the clutch body is engageable with the gearing (26) of said sliding sleeve (25).
 6. A range change transmission according to claim 1, wherein said recesses (31) are U-shaped in transverse cross section.
 7. A range change transmission according to claim 1, wherein said first ratio of said range change transmission is a low ratio and said second ratio of said range change transmission is a through drive.
 8. A range change transmission for a vehicle designed as planetary transmission (2), said range change transmission comprising:a sun gear (3) being rigidly supported adjacent one end of an output shaft (4) of a main transmission; a planet carrier (8), carrying planet gears, being rigidly connected to an output shaft (9) of said range change transmission; a separating clutch having a synchronizing device and an axially movable sliding sleeve (25); a ring gear (6) being concentrically disposed with respect to said output shaft (9) with said ring gear (6) being connectable, via said separating clutch, with a transmission casing (1) to provide a first ratio of said range change transmission and said ring gear (6) being connectable, via said separating clutch, with said output element (8 or 9) to provide a second ratio of said range change transmission; a gearing (26), supported by said sliding sleeve (25), being engageable with a coupling gear (12) supported by said transmission casing (1) when said sliding sleeve (25) is in a first axial end position, and said gearing (26) being engageable with a coupling gear (12) supported by said output element (8 or 9) when said sliding sleeve (25) is in a second axial end position; wherein said synchronizing device comprises a single-piece synchronizer ring (22) with two friction surface (23), one of said two friction surface (23) cooperates with a mating bevel surface (19) of said transmission casing (1) and the other of said two friction surfaces (23) cooperates with a mating bevel surface (18) of said output element (8 or 9); radial pressure members (29) are supported by said sliding sleeve (25) and spring loaded in a direction toward said synchronizer ring (22); ramp-like pressure pieces (30) are situated on the external periphery of said synchronizer ring (22) in recesses (31) formed on both sides of a transverse central plane of said sliding sleeve (25), and said pressure members (29) exert an axial force upon said synchronizer ring (22) in both axial directions of movement of said sliding sleeve (25) via said pressure pieces (30) situated on both sides of the transverse central plane.
 9. A range change transmission according to claim 8, wherein said recesses (31) are U-shaped in transverse cross section.
 10. A range change transmission according to claim 8, wherein said first ratio of said range change transmission is a low ratio and said second ratio of said range change transmission is a through drive. 